The M’s may be planning use Liddi, who played parts of 2011 and 2012 with the major-league club, in the outfield as Michael Morse is now day-to-day with a quad strain. Liddi may also play third base or another infield position, now that Dustin Ackley has been sent to Triple-A and first baseman Justin Smoak is nursing an oblique strain.

Maurer, 22, heads down to Tacoma after another poor start Tuesday in Seattle’s 6-1 loss to the Padres at Safeco Field. In 5 2/3 innings, he gave up six runs on nine hits including two home runs. After 10 starts this season, Maurer is now 2-7 with a 6.93 ERA, having leapfrogged from Double-A to the majors after an impressive spring training.

Liddi, who last year batted .224 in 38 games with the Mariners, joins Seattle after a satisfactory season thus far in Tacoma. The 24-year-old batted .267 with nine homers, eight doubles, two triples and 37 RBIs over 50 games for the Rainiers, mainly playing at third base.

He hasn’t played in the outfield this year, but he occasionally made an appearance in left field in 2012 for the M’s. While Liddi may see time in the outfield, some sports pundits — including Dave Cameron of USS Mariner, syndicated on seattlepi.com — expected the Mariners to call up Franklin Gutierrez, who is rehabbing in Tacoma from a strained right hamstring.

The Mariners said there will be an additional roster move to replace Maurer in the starting rotation before his next scheduled start, which was slated for Sunday against the Twins in Minnesota.